Correctly display stdout and stderr in case a doctest is failing

Author: GuillaumeGomez

src/librustdoc/doctest/runner.rs

@@ -131,7 +131,22 @@ mod __doctest_mod {{
             .output()
             .expect(\"failed to run command\");
         if !out.status.success() {{
-            eprint!(\"{{}}\", String::from_utf8_lossy(&out.stderr));
+            if let Some(code) = out.status.code() {{
+                eprintln!(\"Test executable failed (exit status: {{code}}).\");
+            }} else {{
+                eprintln!(\"Test executable failed (terminated by signal).\");
+            }}
+            if !out.stdout.is_empty() || !out.stderr.is_empty() {{
+                eprintln!();
+            }}
+            if !out.stdout.is_empty() {{
+                eprintln!(\"stdout:\");
+                eprintln!(\"{{}}\", String::from_utf8_lossy(&out.stdout));
+            }}
+            if !out.stderr.is_empty() {{
+                eprintln!(\"stderr:\");
+                eprintln!(\"{{}}\", String::from_utf8_lossy(&out.stderr));
+            }}
             ExitCode::FAILURE
         }} else {{
             ExitCode::SUCCESS

tests/rustdoc-ui/doctest/edition-2024-error-output.stdout

@@ -5,6 +5,9 @@ test $DIR/edition-2024-error-output.rs - (line 12) ... FAILED
 failures:
 
 ---- $DIR/edition-2024-error-output.rs - (line 12) stdout ----
+Test executable failed (exit status: 101).
+
+stderr:
 
 thread 'main' panicked at $TMP:6:1:
 assertion `left == right` failed
@@ -13,6 +16,7 @@ assertion `left == right` failed
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 
 
+
 failures:
     $DIR/edition-2024-error-output.rs - (line 12)